Walk-in cooler problems

[Louis Teo]

I have a flower walk-in cooler and the compressor is Tecumseh AJ137ET-193 J7/AJA4512YXD 134a. The room is not cold. Found both condenser and evaporator coils very dirty. Cleaned both up but room remains warm. System symptoms are as follows; Distributor pipes after expansion valve just slightly cool(same for evaporator outlet pipe), top of compressor canister is cool while inlet pipe to condenser is just warm and condenser outlet pipe is slightly cool. Low noise level from compressor and slightly bubbling at liquid sight glass. Topped up refrigerant till no more bubbling at sight glass. Occasionally, evaporator outlet pipe freezes all the way to the compressor. When this happens, compressor noise level goes up and room becomes cool but it happens rarely.
Thought expansion valve was erratic. Changed it but situation remains the same.
I doubt a small hermetic compressor as this one have loading and unloading capability. What is the problem.
Is there a solution without having to replace the compressor?

[chemi-cool]

To check the compressor valves you need to close the suction valve or receiver valve and pump it down to about 0 psi. If it holds the pressure, the valves are OK.
you can check the discharge by closing the discharge valve slowly while compressor is running and see if the pressure goes up and cut on high pressure switch.

When suction pipe freezes, from returning liquid, check the superheat or orifice size.

[Grizzly]

Lois you need a fridge engineer to check it out for you.
5 Min's with a set of gauges, a thermometer and comparator.
Should confirm your problem.
But then again how come you are topping up the system but listed as a retailer.
Check your superheat as it could be your expansion device?
Grizzly

[Louis Teo]

Thanks for your advice. Many years ago, I worked on large Dunham Bush's water chillers for a short while but never on small systems. Am now semi-retired, running a flower shop which I bought and it came with a walk in cooler together with a small bottle of left over refrigerant and charging pipe and nothing else. I do not have a charging manifold to check pressures.
Missed out mentioning this;
1)Temperature before and after filter drier feels the same. Don't suspect chokage.
2)Pipes close to compressor now rattle noisily, not like before.
3)System was running trouble free for a few years and nobody touched the expansion valve and it flooded the the evaporator ocassionally. I changed the expansion valve but all symptoms appear to remain the same.
My suspicion is that when the condenser was running dirty, the high discharge temperature was burning oil depositing carbon on the discharge reed valves so that they are now leaking. I hate to have to replace the compressor. Need advice from so many experts out there. If my suspicion is accurate, is there any product nowadays to free sticky/leaky valves, some kind of oil additives that could be introduced into the system like leak detection dyes?

[Gary]

What are the air on and air off temps for both the evaporator and the condenser?

[Gary]

Occasionally, evaporator outlet pipe freezes all the way to the compressor. When this happens, compressor noise level goes up and room becomes cool but it happens rarely.

I would suspect moisture in the system, freezing and blocking the flow, then thawing occasionally and flooding through. If you didn't change the drier when you changed the TXV, shame on you.

[Louis Teo]

Hi Gary,
Thanks for your advice. My response is as follows;
1)There was no palpable temperature difference before and after filter drier. So, didn't change it. Besides, there are no isolation valves. Will need a vacuum pump which I don't have. Quit this trade many years ago and don't hold a license which is required for purchasing of equipment,instruments and spare parts.
2)Will go find a thermometer to get the on/off coil temps and get back to you.
3)System has been behaving good for many years and no work has been done on it. Is it possible to have moisture ingress during this trouble free period when the system had not been worked upon? There is no frost anywhere on or near the outside of the TX valve at all. Is it still possible to have frozen moisture blocking the TX valve orifice? Actually, the only time there is frost after the TX valve, at the distributor, is when flooding occurs, which is rare.

[Gary]

Not knowing the pressures and temperatures makes trouble shooting very difficult.

Are there any devices in the liquid line?... have you checked for kinks in the lines?

Are there any devices between the evap and the compressor?... perhaps an EPR valve?

[Louis Teo]

There is a liquid solenoid valve close to TX valve and there's no EPR or any other devices between evap and compressor. There is no palpable temperature difference before and after the solenoid valve and there are no kinks in any of the pipe lines, liquid or vapor. Compressor sump is cool, just like the canister top.
Just got the temp. readings as follows:-
Off evap- 55 F
On evap- 56 F
Off Cond - 70 F
On cond - 56 F

[Gary]

Since there is a solenoid valve, we can assume it is designed for pumpdown. A restriction would cause it to pump down. This is looking more and more like the compressor valves are gone.

[FEISTY]

Unless I misunderstood your description of your previous repairs, you don't have a vacuum pump so how did you evacuate the system before recharging it ? Next having comparable temperatures before and after the dryer doesn't explain why , after the system was opened to atmosphere and exposed to moisture, a new filter dryer wasn't used. I explain to customers when I discover a previous service company did the same shortcut that it equates to changing the oil in your car but not the filter. Lastly...being a former serviceman, how do you even start any evaluation without a manifold ???. Very possible you have air in system which could explain the rattling in the pipes. Start from the beginning....the very beginning. Re-equip yourself, re-license yourself or call a qualified certified serviceperson. Cheaper...and safer in the long run.

[Louis Teo]

This reply is to address Feisty's queries. This recent work done on the system did not require evacuation because the sight glass showed just a little bubbling. So I just topped it up a little.When I recently changed the TX valve, liquid solenoid valve was closed and I had the refrigerant bottle connected at the compressor suction valve purging out a little refrigerant vapor backwards through the evaporator and exiting out from the distributor while I connected up the replacement TX valve. Before tightening up the connections, I energised the solenoid valve momentarily. I have no resources, just spanners and screwdrivers. This job was done with wits only.
I tend to concur with Gary that the valves may be kaput. So, my question is if there's any product that could be pumped into the system to free up the valves.

[Louis Teo]

This reply is in response to Chemi-cool's good advice.
Will do as suggested once I can get hold of a charging manifold.

[monkey spanners]

There is no magic valve aditive to fix a bad compressor, only a replacement part.

[Louis Teo]

OK guys, thanks for all your advice and wisdom. Much appreciated.